Overall Description
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This webpage is a summary of my Bachelor of Engineering Thesis.
If you would like to see plots, just go to the next page. Otherwise, this is a short introduction so this can be understood in a glimpse.
The point of my thesis was to build a magnetic field sensors that uses an optical fibre. This was accomplished by building different types of interferometers, with ferrofluid reacting with magnetic field.
The sensor with a ferrofluid-filled capillary described in this paper has not been previously described in literature, or I couldn’t find any.
Interference:
When two waves of light meet each other, and their lenghts match, they can add or substract from each other. This is called interference. This act can happen for a whole range of wavelengths. In our case, the light can interfere when it is inside of a capillary.
Used items:
A cappilary, or “no core fibre” is just a tiny little pipe, made our of glass. It has a small hole inside, and we assume that it’s inside and outside circumference is always of the same size.
A ferrofluid is a fluid, filled with tiny particled that react with magnetic field. That way, we can change the most important property - the angle by which light gets reflected - using magnetic field. In my study, I tested two ferrofluids made by Ferrotec company.
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The princible - summing up:
By placing a cappilary in a ferrofluid, we can alter its optical property using magnetic field. That way, and adding that each wavelength refracts at a slightly different angle, we can measure changes made to a wide spectrum of light by a
1st Sensor Type
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Base plot - whole range of wavelengths, each series has magnetic induction increased:
Above plot, zoomed at the area of interest:
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Basic schema for how the sensor works:
As the magnetic induction changes, the each wavelengths refracts at slighly different angle